The phases of the Moon are the different ways the Moon looks from Earth over about a month. As the Moon orbits around the Earth, the half of the Moon that faces the Sun will be lit up. The different shapes of the lit portion of the Moon that can be seen from Earth are known as phases of the Moon. Each phase repeats itself every 29.5 days.
The same half of the Moon always faces the Earth, because of tidal locking. So the phases will always occur over the same half of the Moon's surface. A phase is an angle of the moon to the earth so it appears differently every day.
There are four major moon phases as moments in time during the lunar cycle of 29.53058770576 days.
- New Moon = 0 days
- First Quarter = 7.38264692644 days
- Full Moon = 14.76529385288 days
- Last Quarter = 22.14794077932 days
- New Moon = 29.53058770576 days = 0 days
There are four other moon phases as periods in between: waxing crescent, waxing gibous, waning gibous, and waning crescent.
The Moon goes through 8 total phases in its 29.53 days of cycle where each individual phase correspond to a moon age period and a moon cycle fraction.
- A new moon is when the Moon cannot be seen because we are looking at the unlit half of the Moon. The new moon phase occurs when the Moon is directly between the Earth and Sun. A solar eclipse can only happen at new moon.
- Period: 0 to 1 day
- Fraction: 0 to 0.033863193308711
- Period: 28.53058770576 to 29.53058770576 days
- Fraction: 0.966136806691289 to 1
- A waxing crescent moon is when the Moon looks like crescent and the crescent increases or waxes in size from one day to the next. This phase is usually only seen in the west.
- Period: 1 day to 6.38264692644001 days
- Fraction: 0.033863193308711 to 0.216136806691289
- The first quarter moon or a half moon is when half of the lit portion of the Moon is visible after the waxing crescent phase. It comes a week after new moon.
- Period: 6.38264692644001 to 8.38264692644 days
- Fraction: 0.216136806691289 to 0.283863193308711
- A waxing gibbous moon occurs when more than half of the lit portion of the Moon can be seen and the shape increases or waxes in size from one day to the next. The waxing gibbous phase occurs between the first quarter and full moon phases.
- Period: 8.38264692644 days to 13.76529385288 days
- Fraction: 0.283863193308711 to 0.466136806691289
- A Full Moon is when we can see the entire lit portion of the Moon. The full moon phase occurs when the Moon is on the opposite side of the Earth from the Sun, called opposition. A lunar eclipse can only happen at full moon.
- Period: 13.76529385288 to 15.76529385288 days
- Fraction: 0.466136806691289 to 0.533863193308711
- A waning gibbous moon occurs when more than half of the lit portion of the Moon can be seen and the shape decreases or wanes in size from one day to the next. The waning gibbous phase occurs between the full moon and third quarter phases.
- Period: 15.76529385288 to 21.14794077932 days
- Fraction: 0.533863193308711 to 0.716136806691289
- The last quarter moon or a half moon is when half of the lit portion of the Moon is visible after the waning gibbous phase.
- Period: 21.14794077932 to 23.14794077932 days
- Fraction: 0.716136806691289 to 0.783863193308711
- A waning crescent moon is when the Moon looks like the crescent and the crescent decreases or wanes in size from one day to the next.
- Period: 23.14794077932 to 28.53058770576 days
- Fraction: 0.783863193308711 to 0.966136806691289
A second full moon in one calendar month is usually called a blue moon and this occurs approximately every 3 years.
A supermoon or Super Pink Moon takes place when moon's orbit is at its closest to the Earth. Supermoon take place each year between March and May.